Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$183.30	8.700%	$199.2471	$199.25	$199.25	$199.20
Purchase #2	$210.40	4.150%	$219.1316	$219.13	$219.15	$219.10
Purchase #3	$88.85	7.559%	$95.5662	$95.57	$95.55	$95.60
Purchase #4	$83.28	4.396%	$86.941	$86.94	$86.95	$86.90
Purchase #5	$126.39	13.146%	$143.0052	$143.01	$143.00	$143.00
Purchase #6	$130.72	11.270%	$145.4521	$145.45	$145.45	$145.50
Purchase #7	$82.52	5.800%	$87.3062	$87.31	$87.30	$87.30
7 purchase totals =	$905.46		$976.6494	$976.66	$976.65	$976.60